The invention relates to a reciprocating piston engine with an externally supplied ignition, i.e., spark ignition, and at least one inlet port per cylinder, each of which can be closed and opened by an inlet valve, which is associated with a conduit-shaped inlet for air and/or a fuel-air mixture and which is connected with means which enable a controllable deflection of flow at the transition from the inlet through the inlet port into the cylinder.
WO 91/14858 discloses an engine of the above-described type. The means for deflecting the flow in the prior device are comprised of slides, butterfly valves, swivel nozzles, or the like, which are disposed in the conduit-shaped inlet, immediately upstream of the inlet port. These elements are actuated via corresponding actuation means, depending upon the operational state of the engine, in order in certain operational states to deflect the fuel-air mixture, always referred to below as gas flow, which is flowing through the conduit-shaped inlet, so that during the intake stroke, inside the cylinder space, a rolling vortex is formed, whose rotational axis runs perpendicular to the cylinder axis. The disadvantage of this apparatus is comprised in that the actuation means are disposed and supported in the inlet directly upstream of the inlet port, that is, in a region in which there is only a small amount of space available for additional elements.
The object of the invention now is to improve a reciprocating piston engine of the kind described at the beginning with regard to the deflection possibilities of the gas flow upon entry into the cylinder.
This object is attained according to the invention by the fact that the inlet has at least a first and a second partial conduit, which join together to form an inlet region immediately upstream of the inlet port. The dividing plane is aligned essentially perpendicular to the axis of the cylinder, that at least the first partial conduit is connected to the fuel supply, and that means are associated with at least the second partial conduit, which are for changing its free flow cross section. This apparatus has the advantage that the flow through at least one of the partial conduits is purposefully supplied to a section of the valve gap region and the distribution over the valve gap of the charge mass flowing into the cylinder can be changed by throttling at least one of the partial flows. Since the distribution of the charge mass over the valve gap has a determining influence on the development of a vortex in the cylinder, in the end the vortex development and vortex intensity in the cylinder can be controlled by the throttling of at least one of the partial conduits. At the same time, there is the possibility of influencing the degree to which the various ingredients in the charge mix. The mass distribution onto the upper and lower valve gap region is influenced by means of this. At a greater percentage by mass, a rolling vortex (tumbling) is formed in the cylinder of the engine by means of the upper valve gap region, which vortex can favorably influence combustion and, if desired, makes possible a stable layering between air, fuel, and/or exhaust. The vortex development when the lower partial conduit is closed furthermore leads to a favorable combustion behavior at low engine loads (partial load). At full load, no intense vortices should be produced, i.e., both partial conduits should be open. The particular advantage of this device is comprised primarily in that the means for changing the free flow cross section do not have to be disposed directly upstream of the inlet port, but with a certain spacing from it so that greater embodiment possibilities in construction are available here.
A further advantage of the invention is comprised in that the necessary built-in parts in the inlet conduit reduce the free flow cross section only slightly so that only slight additional flow losses occur. Already for structural reasons, the preferably upper first partial conduit is connected to the fuel supply, for example in the manner that a fuel injection nozzle discharges into this conduit. Depending on the operational state, at this point, when the second partial conduit is closed or only slightly open, the fuel-air mixture flows through the upper, first partial conduit and is principally supplied to the upper valve gap region. To the extent to which the supply of air or also of exhaust is increased via the second partial conduit disposed beneath it, the charge mass supplied to the lower valve gap region is also increased, so that the vortex development in the cylinder is reduced in accordance with the increase of the gas flow through the second partial conduit. The end edge of the dividing plane can be guided in until it seals against the shaft of the inlet valve or otherwise guided in so that the flow through the first (upper) partial conduit is conducted directly into the upper region of the valve gap. By means of this, a powerful rolling vortex is produced in the cylinder itself. The intensity of the rolling vortex can be varied in infinitely graduated fashion by controlling the distribution of the aspirated charge mass onto both of the partial conduits.
The mixing of the fuel-air mixture, or the mixture of exhaust, fuel, and air, can be influenced depending upon the structural embodiment of the conduit division and/or the choice of the time of fuel supply (injection time). In this case, both an intense mixing (homogeneous mixture) and an intense layering of the mixtures can be achieved. The invention furthermore permits the introduction of exhaust into at least one partial conduit and the achievement of a more or less intense layering of the exhaust-fuel-air mixture, depending upon the structural embodiment or the throttling of the partial conduits.
With the disposition of a plurality of inlet valves per cylinder, the invention furthermore, as one alternative, makes it possible to provide a common inlet for all inlet valves, in such a way that for all inlet valves, there is a common inlet region, in which the dividing plane ends. In the same manner, however, it is also possible to provide each inlet valve with an individual inlet, which is divided into two partial conduits.
While it is fundamentally possible to route the partial conduits as individual conduits that do not join together until the inlet region, a preferred embodiment of the invention provides that the inlet is embodied by an inlet conduit which is divided into two partial conduits by means of a dividing wall, at least over a partial length between the fuel supply and the inlet region. An inlet of this kind can already be cast integrally when the cylinder head is manufactured. The dividing wall can be comprised of the casting material of the cylinder head or of a component of another material, which is correspondingly inserted into the casting form and which is securely cast integrally with the cylinder head.
While the change of the flow direction of the gas flow that is flowing into the cylinder can be achieved via a change of the volumetric flow through the second flow conduit, specifically by providing that the conduit cross section is more or less unblocked via corresponding actuation means, in another embodiment of the invention it is possible for the dividing wall to be movably disposed in the inlet conduit--preferably longitudinally movable--and to be connected to a controllable actuation means so that the spacing of its end edge to the inlet port in the inlet region can be changed. As a result, when there is a central influence of the volumetric flow for the inlet conduit upstream of the dividing wall, which can also extend over only a partial length of the inlet conduit, the possibility arises of allowing the deflecting action of the downward directed curvature of the conduit wall to be more or less intensely effective, specifically because the gas flow through the second partial conduit loses the guiding influence of the dividing wall a short or long distance away from the inlet port. In lieu of a longitudinal movement of the dividing wall, which leads to a change of the flow guiding influence of the dividing wall, in particular of the influence of the end edge in the inlet region, in another embodiment of the invention it is possible to dispose the dividing wall in the inlet conduit, so that it can move perpendicular to the dividing plane, and to connect it with correspondingly controllable actuation means. With this device, the influence of the influx direction is likewise carried out by a change of the quantitative proportions of the volumetric flows, which are flowing through the first and the second conduits. If the volumetric flow through the second conduit is increased because the dividing wall is moved perpendicular to its face toward the wall of the first partial conduit and hence the flow cross section of this first partial conduit is reduced, an influx of gas flow into the cylinder is likewise produced, which takes place predominantly in the direction of the inlet conduit, and thereby a corresponding vortex development is generated.
Using the fact that the end edge of the dividing wall in the inlet region is exposed to an increased temperature influence, in another embodiment of the invention, it is provided that a bimetallic vane is disposed in the region of the end edge which is oriented toward the inlet port; the vane closes the flow cross section of the second partial conduit at least partially when the engine is cold and unblocks it as the heat increases. This device has the advantage that the means for changing the flow cross section are also the actuation means, in the form of the bimetallic vane.
In a further advantageous embodiment of the invention, it is provided that the dividing wall can be heated, in particular in a reciprocal piston engine with fuel injection. Since for structural reasons if no other, the unit injector for the fuel cannot be made in the flow direction in the partial conduit, but is made aligned at a certain angle, the disposition of a dividing wall which can be heated, offers the advantage that fuel droplets landing on the dividing wall are vaporized and consequently the mixture formation is improved.